(1) Field of the Invention
This invention relates to a container bag for use in the preservation or transport of blood or the component material of blood at a quite low temperature in the range of -170.degree. to -196.degree. C. More particularly, the invention relates to a container bag which is quite suitable for the use at a low temperature such as -196.degree. C. without the occurrence of tearing owing to the brittleness and is light in weight, produced easily and good in transparency. The container bag is made of an inner layer of ethylene-tetrafluoroethylene copolymer and an outer layer made of a resin selected from the group consisting of polyethylene naphthalate, cross-linked polyethylene, perfluoroalkoxy resin, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and aromatic polyimide.
(2) Description of the Prior Art
In the conventional art, the containers for blood have been made of glass, polyvinyl chloride, polypropylene and the like. In recent years, only a single component of blood such as erythrocyte is used in blood transfusion in view of therapeutics. Further, blood and its components are preserved for a long time and they are used as occasion demands or in an urgent need. That is, the quantity of blood transfusion is now increasing and the long term preservation of blood is desired earnestly.
As the known blood preservation methods, there are ACD blood preservation method (preserved at 4.degree. to 6.degree. C. in glass bottles, polyvinyl chloride containers or polypropylene containers) and slow freezing method (preserved at -80.degree. to -90.degree. C. in polyvinyl chloride containers). In the former method, the available period of the blood is short, for example, about 21 days from the blood-collecting owing to the blood metabolism during the preservation. While, in the latter method, high concentration glycerol is used as an additive for preventing the evil effect in freezing, so that it must be rinsed off and the rate of recovery of erythrocyte after preservation becomes very low. Further, the quality of erythrocyte is reduced in the slow freezing method as compared with the quick freezing method.
The above-described disadvantages have been eliminated in recent years since the quick freezing method was proposed. In the quick freezing method, the blood is instantaneously freezed in liquid nitrogen (-196.degree. C.) and it is preserved at a quite low temperature in the range of -170.degree. to -196.degree. C. In this quick freezing method, however, the problem of blood container is left unsolved and the containers or receptacles which are durable in such a quite low temperature are earnestly desired.
As the preservation containers for the quick freezing method, the foregoing containers made of vinyl chloride and polypropylene are not suitable because they are liable to crack by slight shocks at such a low temperature. The glass containers are broken quite easily, in addition, the thicknesses of the container walls are large, therefore, the glass containers are disadvantageous in view of thermal conductivity in the quick freezing method. Upon this, the containers made of aluminium or stainless steel have been proposed as the blood containers for quick blood freezing, however, the production and the sealing of mouths or openings of these metal containers are quite difficult. If the liquid nitrogen penetrates into the container, the erythrocyte in the container is destroyed. In addition, the metal container is not transparent so that the blood in the container cannot be observed through the wall of the container. Furthermore, since the blood container is used only once and then it is thrown away in blood banks and blood centers, it becomes expensive and cannot be used repeatedly or for various purposes.